Escape any custom CSS to avoid problems with quotes or newlines

autoHeightWebView/index.android.js

@@ -240,9 +240,11 @@ export default class AutoHeightWebView extends PureComponent {
     if (!styles) {
       return script;
     }
+    // Escape any single quotes or newlines in the CSS with .replace()
+    const escaped = styles.replace(/\'/g, "\\'").replace(/\n/g, '\\n')
     return `
       var styleElement = document.createElement('style');
-      var styleText = document.createTextNode('${styles}');
+      var styleText = document.createTextNode('${escaped}');
       styleElement.appendChild(styleText);
       document.head.appendChild(styleElement);
       ${script}

autoHeightWebView/index.ios.js

@@ -94,9 +94,11 @@ export default class AutoHeightWebView extends PureComponent {
       if (!styles) {
         return script;
       }
+      // Escape any single quotes or newlines in the CSS with .replace()
+      const escaped = styles.replace(/\'/g, "\\'").replace(/\n/g, '\\n')
       return `
         var styleElement = document.createElement('style');
-        var styleText = document.createTextNode('${styles}');
+        var styleText = document.createTextNode('${escaped}');
         styleElement.appendChild(styleText);
         document.head.appendChild(styleElement);
         ${script}